Many containers such as pouches and trays vary in the amount of headspace in the container. For example, flexible pouches containing cheese are initially filled with carbon dioxide and nitrogen gas along with the cheese. The gas is absorbed after several hours and the pouch is relatively flat but prior to this and after filling, gassing and initially sealing the pouch a substantial headspace is present due to the unabsorbed gas. The variation in headspace in the pouches influences the leak testing resulting when these containers are enclosed and leak tested in a fixed chamber testing apparatus as in U.S. Pat. No. 5,042,291, for example. There is a need for an improved method and apparatus for testing containers which avoid this disadvantage and which give more consistent test results when testing flexible or semi-flexible packages.
Tyvek packages are used primarily in the pharmaceutical and medical industry to enclose syringes, sponges, and other sterile products that are used by the medical profession in hospitals or surgery rooms. On one side of the package there is usually an impermeable plastic or tray and on the other side is the Tyvek cover or lid, which is a permeable paper so that the contents of the package can be sterilized after the package is sealed. If the seal of the package is not perfect, it could then let go or there could be a seal leak causing loss of sterility. When testing this type of package in the prior art apparatus and according to the prior art method, variable leaks are always measured so the test results are not reliable or consistent, because the Tyvek leak rate or permeability varies from one lot of material to another. There is a need for an improved method and apparatus for leak testing the seals in containers of this type.